Wireless communications devices, including mobile telephones and other portable radio communication devices, can include internal, embedded antennas or external, protruding antennas. Internal antennas have become increasingly popular at least because of their small size, light weight, and aesthetic advantages (e.g., allowing the device to have a sleek outer design). However, the arrangement of antennas within, for example, a mobile phone can be constrained at least due to the limited space that is available for antenna structures. For example, when mounted inside a mobile device, the antennas are often subject to problematic amounts of electromagnetic interference from other metallic or conductive objects within the device, particularly from a ground plane included within the device housing. To minimize such performance-abating interference, the antenna volume (e.g., a three-dimensional space inside the device that can be occupied by an antenna structure) can include “dead space” or a “keepout” clearance to set the antenna structure a requisite distance apart from nearby conductive element(s). In at least this way, a given antenna structure can occupy more space or volume within the mobile phone than just the physical geometry of the antenna structure.
Moreover, the growing demand for connectivity in an increasingly mobile world, and for high speed, high data rate wireless communications, has resulted in mobile communications devices that have an increasing number of antennas, covering multiple frequency bands and both cellular radio access technologies (RATs) and non-cellular RATs (e.g., Bluetooth®, Near Field Communication (NFC), Wireless Local Area Network (WLAN, a.k.a. WiFi), Wireless Metropolitan Area Networks (WMAN, a.k.a. WiMax), Radio Frequency Identification (RFID), Global Positioning System (GPS), etc.). As a result, the internal antenna volume within a mobile phone is often shared by several antennas situated in close proximity, creating antenna design challenges related to isolation, efficiency, and bandwidth.
Antenna design can be further complicated by the need for interoperability between multiple, cellular RATs as existing technologies evolve, or new technologies emerge in parallel to the existing RATs. For example, GSM (Global System for Mobile Communications), EDGE (Enhanced Data Rates for GSM Evolution), UMTS (Universal Mobile Telecommunications System), and LTE (Long Term Evolution) can be considered evolutions of the same platform and are colloquially referred to as 2G, 2.5G, 3G, and 4G technologies, respectively. CDMA (Code Division Multiple Access) can be considered a competing 3G technology that blends into LTE's 4G technology. These different RATs, whether GSM-based or CDMA-based, may require different circuitry components within a printed circuit board of the mobile device. Further, each of the RATs operates within different frequency bands, and each frequency band may be assigned to specific regions of the world and/or specific wireless communications carriers. As a result, global mobile device manufacturers often create carrier, region, and/or RAT-specific versions or variants of their mobile devices to have a presence in various markets around the world.